This invention relates generally to a tuning fork quartz crystal vibrator of the type used in electronic wristwatches and more particularly to a tuning fork crystal vibrator which has a highly favorable cubic temperature characteristic and includes weight added to the tines to correct deviations in the resonant frequencies caused by variations in manufacture. Crystal vibrators of the prior art suffer many deficiencies. Generally speaking, unless elaborate precautions are taken, the resonant frequency of the crystal vibrators is unstable when ambient temperature changes. Also, the Q of resonance is low and the effects of aging on frequency can be significant. Further, many crystal vibrators exhibit a change in frequency output depending on the physical attitude or orientation of mounting. Some of these problems resulting from attitude and aging are minimized by operating the vibrator at high frequencies. However, this has the disadvantage of high power consumption. Additionally, many crystal vibrators of the prior art are not sufficiently small in size as to be suitable for electronic wristwatches, and their dimensional variations in mass production are high, resulting in a low yield of acceptable product and a resultant high cost per unit.
Vibrational frequencies in the range of 100 KHZ are treated herein as "low" frequencies based on comparison with outputs of prior art vibrators of other cuts which are used in electronic timepieces.
What is needed is a tuning fork crystal vibrator which exhibits resonant frequency characteristics which are easily set and stable despite ambient temperature variations. Also, it is desirable that the crystal vibrator have a high Q of resonance, low power consumption, little variation due to aging, orientation and mounting method, extremely small size and good manufacturing yields using mass production techniques.